@media screen and (min-width:321px) and (max-width:375px)
  html
    font-size:14px
@media screen and (min-width:376px) and (max-width:414px)
  html
    font-size:16px
@media screen and (min-width:415px) and (max-width:639px)
  html
    font-size:18px
@media screen and (min-width:640px) // and (max-width:719px)
  html
    font-size:18px
// @media screen and (min-width:720px) and (max-width:749px)
// @media screen and (min-width:750px) and (max-width:799px)
// @media screen and (min-width:800px)